The present invention relates generally to shielded electrical connectors and, more particularly, to an electrical connector having the improved shielding and anti-static effects.
Japanese U.M. Patent Application Kokai No. 61-184285 (the '285 patent) discloses an electrical connector which includes an insulating housing with an annular recess for receiving the shell member or outer contact of a mating connector. A cylindrical shield member fitted in the annular recess has cantilever contact members with a spring free end for contact with a metallic shield of the mating connector. It also has legs projecting from the rear slit to be mounted on a printed circuit board.
Japanese Patent Application Kokai No. 59-143287 (the '287 patent) discloses an electrical connector receptacle which includes a shield member fitted in an annular channel and a flat metal grounding terminal for covering the front end of the receptacle. This electrical connector has EMI and anti-static protection to a certain extent.
However, the front end of the electrical connector of the '285 patent is not covered by the shield member so that interference electromagnetic waves can enter through the front end, causing electromagnetic interference. In addition, if the charged finger contacts the front end, static electricity flows through the contact, causing malfunction in the electrical circuit. Moreover, the mechanical strength of a dielectric material for the front end is lower than that of metals so that the front end is liable to scratch or breakage upon plugging in or out, or by an external force.
The ground terminal of the electrical connector according to the '287 patent consisting of a flat metal sheet and a series of contacts aligned in a cylindrical form has the following disadvantages.
(1) The outer diameter of an annular recess in the insulating housing must be much larger than that of the shell member of a mating connector for receiving the contacts aligned in a cylindrical form. Consequently, when the shell member of the mating connector is plugged in the annular recess, there is a large gap between them. As a result, the contact pin or member can be deformed or bent by an unexpected force applied upon plugging in or out.
(2) The flat metal sheet must be thick for providing mechanical strength while it must be thin for accommodating elastic deformation of the contacts upon plugging in or out. In other words, too thick metal sheets produce poor contacts while too thin metal sheets fail to provide a rigid flat terminal.
(3) Although the flat section does not require any spring property, the contacts must be made from a spring metal so that a spring metal is used to make the entire ground terminal. However, the hardness of such metal is so high that it is very difficult to machine because of spring back, etc. In addition, spring metal is expensive, pushing up the unit manufacturing cost.
(4) Once the ground terminal is attached to the connector and mounted on a printed circuit board, it is so difficult to remove it from the insulating housing that it is almost impossible to replace it with another flat terminal for providing another function such as a different shielding effect, prevention of a wrong connection or adherence of dust and dirt.